Method for mounting a mould for casting a cast part from a metal melt

ABSTRACT

A method for mounting a mould composed of mould parts for casting a cylinder block of an internal combustion engine from a metal melt, includes at least one chill, which forms at least one part section of inner surfaces of a cylinder space of the cylinder block, and is positioned and retained at a wall of one of the mould parts. This method provides for moulds to be mounted with chills provided in a mould cavity. This is achieved by holding the at least one chill in its position at least for a specific duration by magnetic forces, which are exerted by a magnet which is arranged on a side of the wall of one of the mould parts facing away from the at least one chill.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Application of InternationalApplication No. PCT/EP2007/051294, filed on Feb. 9, 2007, which claimsthe benefit of and priority to German Patent Application No. DE 10 2006006 132.2-24, filed on Feb. 10, 2006. The disclosure of the aboveapplications are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to a method for mounting a mould composed of mouldparts for casting a cylinder block of an internal combustion engine froma metal melt, in which at least one chill, which forms at least one partsection of inner surfaces of a cylinder space of the cylinder block, ispositioned and retained at a wall of one of the mould parts.

BACKGROUND OF THE INVENTION

Methods and devices are used on a large technical scale, for example inthe motor vehicle industry, in order to manufacture the cylinder blocksof internal combustion engines in large numbers. In this situation,there is a requirement, especially in the area of cylinder barrels, fora fine-grain, metallurgical microstructure to be constructed which willguarantee a high load-bearing capacity. Another example where aparticularly fine-grain, rapidly solidifying and tough castingmicrostructure is required is the area of a cylinder block in which thebearings for the crankshafts are formed.

In order to obtain rapid solidification in the casting microstructure,in particular in the casting of light metal melts, metal inserts areintroduced into the mould, referred to as “chills”, which include ahighly heat conductive material in order to represent a heat sink, bywhich comparatively large volumes of heat are drawn within a shortperiod of time from the melt coming into contact with the metal inserts.Accordingly, during the casting of cylinder blocks made of aluminumcasting material, chills are arranged in such a way, for example, thatthey form the cylinder barrels in the block which is being cast. Thecasting material coming into contact with the chills arranged in thisway then cools more rapidly than the melt present in the mould which isfurther away from the chills, with the result that the desiredsolidification, characterized by a fine-grain microstructure, takesplace in the area of the barrels.

One example of how metal inserts are introduced into moulds as chills isprovided in DE 195 33 529 C2. In this patent publication, a method forcasting an engine block made of aluminum is described, in which theengine block is cast into a sand mould and its cylinder cavities areformed by chills inserted into the sand mould, wherein these chillsconsist of a brass material, wherein the brass material has acoefficient of thermal expansion of more than 18×10⁻⁶ K⁻¹, adjusted tosuit the coefficient of thermal expansion of the aluminum melt beingcast in each case. Although this method may allow for the desiredmicrostructure to be specifically created in the finished castcomponent, it requires the adaptation of the thermal expansion behaviorof the chills when being heated to the coefficient of thermal expansionbehavior of the aluminum melt. Furthermore, this method has in practiceproved difficult, in certain application situations, for the chills tobe removed from the completed casting after solidification of thecasting material.

Due to the metal inserts' direct effect on the shape retention of theindividual casting, the positioning of the metal inserts must inpractice always be exact, even under the rough conditions of a castingplant. This has often proved to be an elaborate procedure if the mouldas a core package is composed of several mould parts and metal inserts.The term “core packages” is given to casting moulds which are composedof several casting cores. Casting moulds can be easily assembled fromcore packages, with which even complex and filigree mould cavities andtherefore castings can be formed.

A further problem in connection with the use of metal inserts is derivedwhen, as in the example given in DE 195 33 529 C2, the mould is what isreferred to as a “lost mould” which is composed of parts manufacturedfrom a mould material and must be destroyed after the solidification ofthe melt in order to release the finished casting from the mould. Inorder to be able to position the metal inserts used for cooling in suchmoulds in a reliable manner and keep them in position, it is necessaryfor them to be clamped to the moulds, with the mould materialsurrounding them, with the result that after solidification of the meltsthey can only be released from the casting with difficulty.

In order to render the release of the metal inserts easier, it has beencommon hitherto to provide the metal inserts with a ceramic powdercoating, with the intention of reducing the risk of damage to the metalinserts when they are removed from the finished casting. There is notonly additional effort and expenditure involved with the application ofthe coating, this arrangement also has the disadvantage that the heattransfer between the casting metal and the insert is impaired, whichreduces the cooling effect.

In addition to the prior art referred to heretofore, aimed directly atthe assembly of moulds from mould parts and cores, a method and deviceare known from the German Patent Specification 719 454 for themanufacture of cores or mould parts for moulds made of a core compoundor mould compound, which allow for a chill to be retained in theindividual mould or core box in such a way that it stands reliably inthe position intended for it in the individual core or mould part to beproduced in each case. For this purpose, the individual chill isinitially positioned in the empty mould or core box, wherein in thisposition it is in contact in each case with an outer wall of the mouldor core box. By means of an electromagnet, which is located in a cut-outformed from the outside into the wall concerned of the mould box andexerts its effect through the wall section present between theelectromagnet and the chill, the chill is thereafter held in thisposition. Once the filling of the core compound or mould compound hasbeen completed, the excitation current circuit of the electromagnet isswitched off, with the result that the individual mould part or core canbe removed from the box in which the chill is incorporated.

SUMMARY OF THE INVENTION

In one aspect, embodiments of the invention provide a method by whichmoulds can be mounted for casting cylinder blocks with metal insertsprovided in a mould cavity.

One embodiment in accordance with the invention provides a method formounting a mould composed of mould parts for casting a cylinder block ofan internal combustion engine from a metal melt, in which at least onechill, which forms at least one part section of inner surfaces of acylinder space of the cylinder block, is positioned and retained at awall of one of the mould parts. The at least one chill is held in itsposition at least for a specific retention duration by means of magneticforces, which are exerted by a magnet which is arranged on a side of thewall of one of the mould parts facing away from the at least one chill.

This method is suitable for casting light metal melts, for examplealuminum-based melts.

In another embodiment in accordance with the invention, the individualchill, which may also be designated hereinafter as a “metal insert”, isheld by magnetic forces, which are exerted by at least one magnetarranged in a suitable manner, in the position in the mould providedwith regard to its mounting. The chills are themselves magneticallysensitive. Accordingly, the material for the chills is generallyferromagnetic materials, such as iron and its alloys. In particular,chills used in accordance with the invention can be manufactured fromeconomical and wear resistant materials such as cast iron.

In embodiments in accordance with the invention, the magnet bodyexerting the retaining forces on the individual chill during themounting procedure is arranged so that the magnet does not interferewith the casting of the metal melt or other mounting procedures. Forexample, the magnet can be arranged behind the wall at which the atleast one metal insert is positioned in such a way that its magneticforces penetrate through the wall and hold the at least one insertwithout a direct contact between the at least one insert and the magnet.

In another embodiment in accordance with the invention it is no longernecessary to embed the chills in a mould part in order to hold them. Infact, the chills can be handled separately from the mould parts so thatwhen mounting the mould they can be handled like a mould part. Thisleads to a distinct simplification of the production process.

Since the chills in embodiments in accordance with the invention do nothave to be firmly embedded into a mould part or into the respective castpart any more, when removing a mould produced by embodiments inaccordance with the invention there is also no longer the problem ofdamage caused to the chills or the cast part when demoulding. Therefore,the chills do not have to be coated and the amount of preparation can bereduced. Instead, chills in accordance with the invention held bymagnetic forces can be removed easily from the cast part and the mouldparts of the mould after casting. This is advantageous particularly whencasting cylinder blocks of internal combustion engines, also referred toas “engine blocks”, in which the chills represent the contact surfacesof the cylinders.

Embedding the chills, which is required by the prior art duringproduction of the mould parts by surrounding them with mould material ina mould, is not required by embodiments in accordance with theinvention. Due to the fact that the chills are handled separately whenthe mould is assembled and are held in position by magnetic forcesexerted by an individual retaining device, it is possible, in the caseof the use of moulds mounted from mould parts formed from mouldmaterial, to dispense with the need to coat the chills with a finish, asis required with the conventional procedure in order to guaranteeoptimum separation of the individual chill from the cast part producedin each case.

A further advantage of embodiments in accordance with the invention iseasy integration into already existing systems.

Another embodiment in accordance with the invention makes possible themanufacture of cast components in a simpler and more economical mannerthan with the prior art. Such embodiment is particularly well-suited forcasting light metal melts, for example aluminum melts.

The mould parts from which a mould is composed are preferablymanufactured from a mould material which is mixed from a mould basicmaterial and a binder. Basic materials in this situation can be forexample sands containing quartz or free of quartz, whereas binders canbe both inorganic as well as organic binders. Such embodiment isparticularly advantageous if the mould is formed in a known manner as acore package.

The positioning and retaining of at least one chill in the mould can becarried out in another embodiment in accordance with the inventionindependently of any specific preparation of the particular location atwhich the metal part is to be arranged. Accordingly, the positioning ofthe metal part can in each case be carried out at a time which isdetermined solely by the optimum operational sequence in each case onmounting the individual mould. The magnet used for the retention can bearranged in such a way in the area of the at least one chill which is tobe retained that the forces exerted by the magnet will reliably securethe at least one chill.

In an embodiment, an opening (i.e. aperture) may be formed in one of themould parts at the wall of which the at least one chill is positioned,into which the magnet is introduced. With this arrangement of the wallof the individual mould part, the magnet used to retain the at least onechill can be moved into close proximity to the at least one chill inorder to facilitate the mounting process. In particular, when castingengine blocks of which the barrels are represented by chills, it can beof advantage for this arrangement if the mould part is designed in amandrel shape with a blind hole aperture, into which the magnet isintroduced. With this formation of the mould part concerned, a pluralityof chills can be arranged next to one another on the outer surface ofone of the mould parts, so that they form in common the inner shape ofthe individual cylinder and are held jointly by a magnet arranged in thecentral blind hole aperture.

Another embodiment in accordance with the invention is of importance forpractical application, wherein the at least one chill is held in itsposition by means of the magnet until a further mould part is arrangedwhich then holds the at least one chill in its position, by positiveand/or non-positive fit. With this embodiment of the invention, the atleast one chill is held in its position by mould parts mounted after itspositioning without magnetic forces being required for this. A furtheradvantage of this method is that the position of the at least one chillin the mould can be exactly defined by the other parts of the mouldwhich come into contact with the at least one chill in positive and/ornon-positive fit. The retention of the at least one chill by magneticforces therefore serves, in this embodiment of the invention, only foras long as needed to bridge a situation, undefined with regard to theretaining of the at least one chill in the mould, until the individualchill is held in its position by a further mould part, without the needfor any further retention forces to be exerted by a separate retainingdevice.

In general, all magnets are suitable for the application of the magneticforces used for the retaining of the at least one chill in accordancewith the invention provided the magnets can produce a sufficientlystrong magnetic field. Thus, for example, in another embodiment inaccordance with the invention, permanent magnets can be provided inorder to apply the retaining forces in the manner in accordance with theinvention onto the individual chills.

However, if particularly powerful forces are to be applied, and at thesame time a particularly precise control of the magnetic retainingforces needs to be achieved, then an electromagnet is particularlywell-suited. Electromagnets not only allow for an exact adjustment ofthe strength of the magnetic field generated by them in each case, butit is also possible with them, in a simple manner, by switching theelectric power on and off, to determine precisely the time period withinwhich the magnetic forces are applied on the individual chill inembodiments in accordance with the invention. For this purpose, forexample, electromagnets comprising coils can be considered. The magneticfield from such electromagnets can be controlled proportionally to thestrength of the current conducted through the coils.

Another embodiment in accordance with the invention provides for themanufacture of a cylinder block of an internal combustion engineincluding a light metal melt, such as an aluminum or magnesium melt,wherein at least one part section of the inner surfaces of theindividual cylinder space of the cylinder block can be formed by one ormore chills.

Another embodiment in accordance with the invention provides forapplication in a fully-automatic device for assembling a mould in whichdevices such as robots are provided for the handling of the mould parts.Devices in accordance with the invention can position precisely the atleast one chill because the retention of this metal insert in itsparticular position by the magnet is assured, for which no integraljoining of the at least one chill to one of the mould parts is required.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail hereinafter on the basis ofdrawings representing exemplary embodiments. These show in diagrammaticform:

FIG. 1 A first mould part in a section along the section line A shown inFIG. 3,

FIG. 2 The mould part represented in FIG. 1 in a side view, and

FIG. 3 The mould part represented in FIGS. 1 and 2 in a section alongthe section line B shown in FIG. 2.

DESCRIPTION

The mould part 1 formed as a single piece is a constituent part of amould not further represented here for casting a cylinder block for acombustion engine from a melt including an aluminum casting alloy. It ismanufactured in an inherently known manner from a mould material whichis mixed from a mould sand as the basic mould material and a binder andhas a basic section 2, which carries a mandrel section 3 projectingupwards and substantially cylindrical in shape.

The mandrel section 3 has a casing surface 4 which is subdivided by fourradially projecting ribs 5 into four part sections. Included in the areaof the transition of the mandrel section 3 into the basic section 2 ofthe mould 1 is a circumferential groove 6 formed into the upper facesurface 7 of the basic section running around the mandrel section 3aligned substantially at right angles to the circumferential surface 4of the mandrel section 3.

In another embodiment not represented in the Figures, the mandrelsection can also have a casing surface, which is divided by radiallyprojecting ribs into two, three or more part sections. In addition theribs can be designed in contrast to the shape having parallel side wallsrepresented in the Figures conically in cross-section tapering orbroadening out. In another embodiment, the mandrel section can also havea casing surface which is not subdivided by additional ribs. In thiscase the casing surface is entirely surrounded by the chill which is tobe accommodated in each case.

With the embodiment represented in the Figures a blind hole aperture 9is additionally formed into the casting part 1, going outwards from thelower face surface 8 of the basic section 2, opposite the upper facesurface 7, wherein this blind hole aperture 9 extends from the facesurface 8 of the basic section 2 as far as the closure wall 10 of themandrel section 3, forming the face side of the mandrel section 3. Thediameter of the blind hole aperture 9 in this situation is adapted tothe outer diameter of the mandrel section 3 in such a way that only onewall 11 with a low wall thickness is present between the inner faces ofthe blind hole aperture 9 and the casing surface 4, this wall 11 beingsufficient to guarantee the required shape stability of the mandrelsection 3.

Inserted into the blind hole aperture 9 is an electromagnet 12, which issecured to the free end of a rod 13. The rod 13 with the electromagnet12 is part of a device, not further represented in the Figures, for theretaining of metal parts 14, 15, 16, 17, which are put into use aschills by a device not represented in the Figures for positioning at thecasing surface 4 of the mandrel section 3.

The rod 13 with the electromagnet 12 can be moved from a position ofrest by means of an adjustment device likewise not represented in theFigures, in which the electromagnet 12 is outside the blind holeaperture 9, into the operational position represented in FIG. 1, inwhich the electromagnet 12 is fully introduced into the blind holeaperture 9. The supply of the electromagnet 12 with electrical energy iseffected by a control device, not represented in the Figures, whichsupplies electrical energy to the electromagnet 12 when the chills 14-17are positioned, in order to retain them in position.

The height of the chills 14-17 is adapted to the height of the mandrelsection 3. In this context the chills in each case have on their upperand lower narrow sides a web 18, 19, projecting upwards and downwardsrespectively, wherein the lower web 18 engages in the groove 6, so thatthe chills 14-17 are held in that location in positive fit. At the sametime, the chills 14-17 are cambered in such a way that they are locatedflush with the section of the casing surface 4 of the mandrel section 3allocated to them in each case. At the same time, the width of thechills 14-17 is adjusted to the width of the sections of the casingsurface 4 in such a way that the sections of the casing surface 4 arefilled completely by the chills 14-17 located flush with them.

The chills 14-17 are cast as grey cast iron from a cast iron alloy,known under the designation GG20 (as per DIN 1691).

As soon as the chills 14-17 are positioned in the sections of the casingsurface 4, the electromagnet 12 is charged with electrical energy. Themagnetic field which is then generated by the electromagnet 12 acquiresthe chills 14-17, and holds them in position at the casing surface 4 ofthe mandrel section 3.

Next, other parts, not shown in the Figures, of the mould, not shown inthe Figures, are mounted. One of the mould parts, not shown in theFigures, has a groove-shaped mounting into which, after positioning ofthe mould part concerned, the rib 19 engages, wherein the groove-shapedmounting is formed at the upper end of the chills 14-17, such that thechills 14-17 are then also held in positive fit at their upper end. Assoon as this state is attained, the energy supply to the electromagnet12 can be switched off and the rod 13 with the electromagnet 12 can bewithdrawn from the blind hole aperture 9.

On casting the cylinder block in the mould, assembled by using the mould1 and the chills 14-17, the chills 14-17 form the barrels of one of thecylinders of the cylinder block. In this case, the chills 14-17 form aheat sink, which ensures that the aluminum melt coming into contact withthe chills 14-17 solidifies rapidly and forms a fine-grainmicrostructure.

REFERENCE FIGURES

-   1 Mould part-   2 Basic section-   3 Mandrel section-   4 Casing surface of the mandrel section 3-   5 Ribs of the mandrel section 3-   6 Groove-   7 Upper face surface of the basic section 2-   8 Lower face surface of the basic section 2-   9 Blind hole aperture-   10 Closure wall of the mandrel section 3-   11 Wall of the mandrel section 3-   12 Electromagnet-   13 Bar-   14-17 Chills-   18, 19 Webs

1. Method for mounting a mould composed of mould parts for casting acylinder block of an internal combustion engine from a metal melt, inwhich at least one chill, which forms at least one part section of innersurfaces of a cylinder space of the cylinder block, is positioned andretained at a wall of one of the mould parts, wherein the at least onechill is held in its position at least for a specific retention durationby means of magnetic forces, which are exerted by a magnet which isarranged on a side of the wall of one of the mould parts facing awayfrom the at least one chill.
 2. Method according to claim 1, wherein anaperture is included at the wall of one of the mould parts of which theat least one chill is positioned, into which the magnet is introduced.3. Method according to claim 2, wherein one of the mould parts is formedin mandrel shape with a blind hole aperture, into which the magnet isintroduced.
 4. Method according to claim 1, wherein the at least onechill is held in its position by means of the magnet until a furthermould part is arranged which then holds the at least one chill in itsposition by positive and/or non-positive fit.
 5. Method according toclaim 1, wherein the magnet is an electromagnet.
 6. Method according toclaim 1, wherein the magnet is a permanent magnet.
 7. Method accordingto claim 1, wherein the metal melt is a light metal melt.
 8. Methodaccording to claim 7, wherein the metal melt is a melt includesaluminum.